WASHINGTON--Mark Hughes, an internationally known leader in DNA diagnostics, has resigned from Georgetown University after coming under fire for allegedly failing to honor a ban on human embryo research. Until his resignation--which occurred on 24 January but was only disclosed this week--Hughes was director of Georgetown's Institute of Molecular and Human Genetics.

Hughes ran into conflict with the university and his former sponsor, the National Institutes of Health (NIH), over his efforts to diagnose genetic diseases--such as Tay-Sachs disease and cystic fibrosis--in test-tube embryos scheduled for implantation (Science, 24 January, p. 472[2]). By testing the DNA of one cell from an eight-cell human embryo, Hughes could determine whether the embryo would be affected by the disease, giving parents the option of not implanting it.

NIH determined, however, that a congressional ban on human embryo research prohibited it from supporting this work. Hughes says he kept the embryo work separate from his NIH-sponsored studies. But NIH sources say that some of Hughes's NIH-supported staff complained that he involved them in embryo testing. Last October, after inquiring into these complaints, NIH stopped funding Hughes. When this news appeared in the press last month, Georgetown began its own inquiry to determine whether Hughes's work violated the university's policy of not supporting studies that could lead to an embryo being discarded. While the inquiry was still under way, Hughes resigned.

Hughes could not be reached for comment, but Georgetown made public a copy of his resignation letter. "Recent events," Hughes writes, "make clear that I cannot continue my preimplantation genetic diagnosis work while serving as a Georgetown faculty member. This work is of crucial importance to me and, I believe, to prospective parents around the world. Accordingly, I am resigning my faculty position. ..." Hughes adds that he intends to continue his research at other unnamed facilities.

Georgetown issued no statement but released a memo to the faculty from Sam Wiesel, executive vice president for health sciences, noting that the university had accepted Hughes's resignation and had appointed cancer researcher Mark Lippman as interim director of the genetics institute. Weisel's note also praises Hughes for helping to found the institute and recruiting "a number of new faculty."